The present invention relates to a process for deodorizing certain cationic nitrile bleach activators.
European patent application EP 0 464 880 discloses cationic nitrites of the general formula R′R″R′″N+—CR1R2—CN X−, where R1 and R2 are hydrogen or a substituent having at least one carbon atom, R′ is a C1-24-alkyl, alkenyl or alkyl ether group or a group —CR1R2—CN, and R″ and R′″ are each individually a C1-24-alkyl or hydroxyalkyl group and the counterion X− is an organic sulfonate, an organic sulfate or a carboxylate. These compounds are useful as bleach activators in laundry detergents. They act as bleach activators in the sense that they react with hydrogen peroxide present to form a perimidic acid that has a stronger bleach activity than the hydrogen peroxide.
Compounds of this type are usually prepared by reacting aldehydes or ketones (depending on the radicals R1 and R2) with a secondary amine (in which case the radicals R″ and R′″ are bound to the nitrogen atom) and an alkyl metal cyanide. The resultant aminonitrile is then quaternized on the nitrogen atom of the amino group by reaction with an alkylating agent or an alkenylating agent (depending on the radical R′), for example dimethylsulfate, generally, the counterion X− also resulting from the alkylating agent. If desired, this counterion, which is usually chloride, sulfate, hydrogensulfate or methylsulfate, can then be exchanged by solvent ion exchange for another counterion, for example a carboxylate, benzenesulfonate or longer-chain alkylsulfate, as a result of which, as is known, the stability of the compound can be increased. Said patent application EP 0 464 880 proposes carrying out the anion exchange in methanolic or isopropanolic solution. The international patent application WO 02/12175 discloses that the exchange of anions can also be carried out in the presence of water at elevated temperature.
As a result, the target compound, the cationic nitrile, is present in water or, if appropriate, organic solvent, and can be used in this form for bleach-activating purposes. Advantageously, however, in particular for use in particulate laundry compositions or cleaning compositions, it is converted in advance into an additionally more storage-stable particulate form that, in its simplest form, can be achieved by removing the solvent, but usually includes a granulation step and/or encapsulation step. The production of granules having a bleach-activating cationic nitrile and, if appropriate, support material, and/or an encapsulation layer, is disclosed, for example, by the German patent applications DE 197 40 669, DE 197 40 671, DE 100 38 086, DE 100 38 823, DE 100 38 845, or DE 100 49 237.
After preparing the target compound, it can be advantageous to improve the odor of solutions or particles which comprise the active substance. Possible causes of odor are, for example, starting materials used in synthesis that remain as impurities, as well as the target compound itself.
The present invention is intended to provide a remedy by means of a treatment step which reliably prevents the occurrence of odor, or at least reduces this below the threshold of perception.
Customary processes for removing volatile components, for example steam distillation under, if appropriate, reduced pressure, do not lead to success on their own, or require an unacceptably long time.
Surprisingly, it has been found that deodorization is simply and reliably possible by using certain oxidizing agents.